1. Field of the Disclosure
The present disclosure relates to an electronic circuit module having a metal cover, and more specifically, it relates to an electronic circuit module in which deformation of a thin metal cover can be prevented.
2. Description of the Related Art
An electronic circuit module is a circuit module in which a high-frequency circuit or the like is formed by a circuit board on which electronic components are mounted. It is built in an electronic device and is used, for example, as an electronic circuit module forming a radio transceiver circuit. It is easy to mount a plurality of electronic circuit modules on a larger-scale circuit board (mother board).
Examples of such an electronic circuit module include a high-frequency tuner module described in US 2008/0174984. FIG. 9 shows a perspective view of the high-frequency tuner module 101 described in US 2008/0174984. As shown in FIG. 9, the high-frequency tuner module 101 includes a circuit board 120 made of a ceramic material, and a shield cover 130 that covers circuit components 110 mounted on a board surface 120a and blocks interfering waves. The shield cover 130 is formed by bending a thin metal sheet into a substantially case shape, and its base surface 131 is disposed parallel to the board surface 120a of the circuit board 120.
The distal ends of four corner side walls 133 of the shield cover 130 are in contact with the four corners of the circuit board 120. By fixing the corner side walls 133 to the circuit board 120, the shield cover 130 is positioned with respect to the board surface 120a of the circuit board 120 in its height direction. Four side walls 132 of the shield cover 130 that are provided so as to correspond to end faces 120b of the square-shaped circuit board 120 are provided so as to extend beyond the board surface 120a of the circuit board 120 along the end faces 120b of the circuit board 120 (in the thickness direction of the circuit board 120).
The shield cover 130 is formed of a metal material. The corner side walls 133 are soldered to GND wires disposed in the four corners of the circuit board 120. The shield cover 130 is thereby fixed to the circuit board 120 and electrically connected with the GND of the circuit board 120. The shield cover 130 covers the circuit components 110 and the like mounted on the board surface 120a of the circuit board 120 and blocks interfering waves from the outside.
As described above, in an electronic circuit module such as a high-frequency circuit, a shield cover (metal cover) is used for blocking electromagnetic waves from the outside. Such a metal cover for blocking electromagnetic waves is often provided so as to cover circuit components (electronic components) mounted on a circuit board, and joined to GND wires (ground wires) of the circuit board. As well as blocking electromagnetic waves from the outside, it prevents high-frequency noise generated by the circuit operation of the electronic circuit module, such as a high-frequency circuit, itself from propagating to the outside.
In recent years, miniaturization of electronic components and development of component mounting technology have progressed, and the area of circuit boards on which electronic components are mounted has been reduced. In an electronic circuit module having a circuit board on which electronic components are mounted and a metal cover, in addition to reduction of the area of the circuit board, miniaturization is required in the height direction. For this reason, the metal cover is provided in such a manner that the clearance between the metal cover and the electronic components is reduced in accordance with the height of the electronic components mounted on the circuit board, and the thickness of the metal sheet from which the metal cover is made has decreased.
However, an electronic circuit module employing a thin metal cover has a problem that the metal cover before joining to the circuit board is deformed owing to drop or external force. The metal cover is formed by cutting and bending a metal sheet by pressing or the like. If the metal cover is dropped or subjected to external force after processing, the metal cover is deformed.
When the metal cover is joined to the circuit board, and if the metal cover before joining to the circuit board is deformed, there is fear that the metal cover is not soldered to the desired position and is soldered to an adjacent different wire. If the deformed metal cover is joined, there is fear that the metal cover is not properly positioned in the height direction and the top plate comes into contact with the electronic components at the time of joining the metal cover.